Transmitting apparatus for inductive carrier railway train communication systems



May 3 Thebnsmzflen B. c. VAN GILDER 2,469,138 TRANSMITTING APPARATUS FOR INDUCTIVE CARRIER RAILWAY TRAIN COMMUNICATION SYSTEMS Filed July so, 1947 L4 2137: RT Receive]? v I lYJ I I I l Main Line T3] System.

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Patented May 3, 1949 UNITED STAT TENT OFFICE TRANSMETTING APPARATUS FOR INDUC- TIVE CARRIER RAILWAY TRAIN COMMU- NICATION SYSTEMS Application July 30, 1947, Serial No. 764,608

Claims.

My invention relates to transmitting apparatus for inductive carrier railway train communication systems, and more particularly to such transmitting apparatus for eliminating interference between nearby systems.

There are two general classes of inductive carrier communication systems for railway trains, namely, systems for use by main line trains and systems for use at terminals. In main line systems telephone communication is generally provided between the two ends of a train, between different trains and between wayside stations and trains en route. In a yard or terminal system telephone communication is provided between a yard ofiice and the switching locomotives operating in the yard. Also, at terminals test tracks are sometimes provided and equipped with apparatus for testing the train communication equipment of locomotives and other vehicles before the locomotive and such other vehicles are sent out on the road.

It is clear that a main line system may extend through or along a yard or terminal system or near a test track since the main line tracks extend through yards and terminal areas. This means that provision must be made so that a yard or terminal communication system or the equipment at a test track does not interfere with the main line system.

In many cases it is desirable when a yard system and a main line system are installed on the same railroad that both systems use the same carrier frequency, for in that way only one equipment needs to be installed on a locomotive in order that the locomotive may be used part time as a switcher and part time for main line work, and the locomotive communication equipment will cooperate with whichever system is at the time involved.

In View of the foregoing problems in communication systems for railway trains, a feature of my invention is the provision of transmitting apparatus for railway train communication systems incorporating novel means to avoid interference between the equipment used for a local area, such as a yard or test track, and a system used for a general area, such as a main line track.

Other objects, features and advantages of my invention will appear as the specification progresses.

The foregoing objects, features and advantages of my invention are obtained by the provision of a main and an auxiliary output circuit for a transmitter of the local area communication system involved. The auxiliary output circuit is related with the wayside transmitting channel of any nearby or adjacent general area communcation system in such a manner that it cancels and balances out the unwanted energy inadvertently applied to such nearby system from the main output circuit of the transmitter.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic View showing one form of apparatus embodying my invention when used to avoid interference between a yard communication system and a main line communication system.

It is to be understood that my invention is not limited to this one application and this one application serves to illustrate the many places the apparatus is useful.

Referring to the drawing, the reference character RT designates a main line track of a railway. This track may be that of a single track railway or it may be one track of a multiple track road. This stretch of railway may be of different lengths, and I shall assume by way of illustration that this stretch of railway has a length of the order of 35 miles. This stretch of railway is provided with a main line train communication system, one function of which is to provide telephone communication between a wayside station PS and trains en route through the stretch, one train being indicated conventionally at TRI and which train has a locomotive LT that is equipped with telephone apparatus. The wayside station PS may be at any suitable point along the stretch of railway and as shown it is near the west or left-hand end of the stretch. The train TRI may be operating at any point within the limits of transmission of the communication system from the station PS and as shown the train is near the east or right-hand end of the stretch.

The reference characters LI and L2 designate a pair of line wires extending along this stretch of railway. The line wires Li and L2 may be wires strung on the usual pole line along the railway right of way and are mounted so as to be parallel to and relatively close to the track RT throughout the stretch of railway. The line wires LI and L2 may be existing wires used in a telegraph or similar circuit and are used in the communication system as an additional service without interference with their present use. These wires Li and L2 may be installed for use in the train communication system alone, and

when thus used one wire may be suificient and the second wire omitted.

The longitudinal circuit of the line wires LI and L2, that is, the circuit including the line wires in multiple and their distributed capacitance to ground, is an element of a transmitting channel for the inductive carrier train communication system provided for this stretch of railway. Such a transmitting channel for railway train communication systems is disclosed in Letters Patent of the United States No. 2,064,642, granted December 15, 1936, to Paul N. Bossart, for Railway train communication systems, and reference is made thereto for a full understanding of such a transmitting channel. It is sufficient for the present application to point out that a carrier telephone current applied to this transmission channel at any point is transmitted along the railway and is available for influencing cooperating telephone receiving apparatus electrically coupled to the transmitting channel. For a train the telephone current is transferred between the apparatus on the train and the wayside transmitting channel by circuit elements mounted on the train for inductive relation with the longitudinal circuit of the line wires and with the track rails which also are an element of the transmitting channel. At a wayside station equipped with telephone apparatus, transmission is efiected by coupling the apparatus to the longitudinal circuit of the line wires. 1

At the wayside station PS, the telephone communication apparatus includes a transmitter TN shown in block form since it can be any one of several well-known arrangements. This transmitter TN may be similar to that disclosed in an application for Letters Patent of the United States, Serial No. 575,311, filed January 30, 1945, by Paul N. Bossart, for Railway train communication systems, and which transmitter is operable to supply a frequency modulated carrier telephone current, the carrier being, for example, one having a frequency of 88 kc., although other carrier frequencies can be used. This transmitter TN is coupled to the longitudinal circuit of line wires LI and L2 through an output transformer Tl, a primary winding ill of which is connected to the output of the transmitter TN and a secondary winding ll of which transformer has one terminal connected to ground electrode 84 and its other terminal connected to the junction terminal of capacitors i2 and it connected in series across the line wires Li and L2. Thus, when the transmitter TN is made active its frequency modulated carrier telephone current is applied to the longitudinal line circuit and the current flows in this line cir,cuit each side of the station and is eifective for infiuencing any receiving apparatus that is inductively coupled to the transmitting channel within the limits of transmission.

The communication apparatus for the locomotive LT of train TR! includes a receiver RC shown in block form. This receiver RC may be similar to the receiver disclosed in the aforementioned Bossart application, and in any event the receiver is operable to demodulate the carrier telephone current supplied by the transmitter TN at station PS and to reproduce the voice frequencies thereof. The receiver RC is connected to a pick-up coil PC which is mounted on the locomotive for inductive relation with the longitudinal line circuit and with the track rails. That is, this pick-up coil PC is inductively coupled with the wayside transmitting channel of the communication system. It follows that the operator at the station PS can talk to the engineman in the locomotive LT through the main line communication system, the longitudinal line circuit of the line wires LI and L2 being an important element in the transmitting channel of the system.

In practicing the invention the locomotive LT 'may be provided with a transmitter similar to the transmitter TN and coupled to the transmitting channel and the station PS may be provided with a receiver similar to the receiver RC and coupled to the longitudinal line circuit. In this way two-way conversation between the station operator and the engineman can be effected. However, the locomotive transmitter and the station receiver are omitted for the sake of simplicity since they are not required for a full understanding of my invention.

Furthermore, when another vehicle of the train TRI or a vehicle of some other train is provided with communication apparatus similar to that provided for the locomotive LT, communication can be efiecte'd between such second train vehicle and the locomotive LT or the station PS.

A dotted rectangle LA indicates in a general way a local area at some point along this stretch of railway, and which local area is provided with a local train telephone communication system. It is to be understood that this local area has no sharply defined limits and it is indicated by dotted rectangle LA as an aid in the understanding of the invention. As here shown the local area comprises a yard YD which may be a classification yard including an incoming track HT and several classification tracks CT, the incoming track HT having connection to the main line track RT and the yard tracks CT being connected to the track HT by a ladder track of the usual construction. The yard YD may be of the hump switching type or may be of the fiat switching type. Ordinarily a train is brought into the track HT and the cars are switched therefrom to the difierent tracks CT according to the destination of the car.

This yard YD is provided with an inductive carrier telephone system to enable the yardmaster or. conductor located at a yard office CF to talk directly to the enginemen of the locomotives within the yard in order to direct the switching operations. To this end the yard ofiice OF is equipped with a carrier telephone transmitter shown conventionally at TN l and which transmitter may be similar to the transmitter TN of the Wayside station PS of the main line communication system. Under this arrangement the transmitter TN l is operable to send out a frequency modulated carrier telephone current, the carrier being here assumed to have a frequency of 88 kc. For reception, each locomotive used for switching about the yard would be equipped with a receiver and pick-up coil similar to the receiver RC and pick-up coil PC of the locomotive LT. That is, the locomotive LT could be used in the yard YD for switching, and its communication apparatus would effectively respond to the transmitter TNI of the yard communication system. 7

This yard communication system is provided with a transmitting channel that includes a line wire L3, which is preferably strung on a pole line to extend the full length of the yard or local area included in the local communication system. Preferably, one end at least of the line wire L3 remote from the yard oifice is connected to at least one rail of each track in the yard. As here shown in the drawing the righthand end of the line wire L3 is connected to the track rails.

The transmitter TN l is provided with a primary and a secondary or auxiliary output circuit. An output transformer T2 is provided with a primary winding H! which is connected to the output of the transmitter TNI and with a secondary winding 15 having two portions one of which is connected to a primary output circuit and the other portion of which is connected to an auxiliary output circuit. The primary output circuit can be traced from the lower outside terminal of secondary winding 15 through an adjustable capacitor ll, an adjustable inductance 13, line wire L3, track rails, ground path, ground electrode I6 and to an intermediate terminal of secondary winding l5. Thus when the transmitter TNl is made active. frequency modulated carrier telephone current is supplied to the transmitting channel for the yard communication system and the current is available for influencing receiving apparatus mounted on locomotives operating within the yard. The phase angle and the magnitude of this current supplied to the transmitting channel for the yard system can be adjusted through the capacitor H and inductance Iii.

Ordinarily such yard communication system would be of a one-way type providing communication from the yard oflice to the locomotive, but it is clear that the locomotive can be provided with a transmitter and the yard olfice with a receiver and the system arranged to provide twoway communication.

In practicing the invention at relatively large yards the line wire L3 may be arranged with multiple branches run to different parts of the yard to bring the transmitting channel relatively close to each track of the yard. In any event the effective area of this yard communication system will be limited as illustrated by the dotted rectangle LA.

It is apparent that this transmitting channel for the yard communication system may not be far removed from the line wires Li and L2 of the main line communication system because the pole line on which the line wires LI and L2 are strung will necessarily be close to certain por-- tions of the yard. This means that the communication current supplied to line wire L3 of the yard system may create a magnetic field that will envelope the line wires Li and L2 and induce therein electromotive forces corresponding to the communication current supplied to the transmitting channel of the yard system. These unwanted electromotive forces induced in the line wires LI and L2 will create a current flow in the longitudinal circuit thereof and such current will tend to influence the receiver BC or" the train TRI when the train is moving within the vicinity of the yard. In other words, the current of the yard communication system will tend to interfere with the main line system when trains are within the vicinity of the yard.

To avoid such interference an auxiliary output circuit is provided for the transmitter TNI as stated hereinbefore, and which auxiliary output circuit extends from the upper outside terminal of primary winding I5 of transformer T2 through an adjustable capacitance l9, adjustable inductance 20, an auxiliary line conductor LG, a capacitor 2| and ground path to the intermediate terminal of secondary winding l5. This auxiliary line conductor L4 is mounted relatively close to the line wires LI and L2. For example, the line conductor L4 may be mounted on the same crossarms as the wires LI and L2 midway between them. The conductor L4 would be of any suitable length, such as, say, 1000 feet. One end of the line conductor L4 would preferably be grounded through capacitor 2 I, as stated above, but the distributed capacitance of line conductor L4 to ground may be sufficient and the capacitor 2| may not be required.

It is apparent that a part of the communication current supplied by transmitter TNI will flow in the line conductor L4 and induce corresponding electromotive forces in the two line wires LI and L2 tending to cause a corresponding current to flow in the longitudinal circuit of the line wires Li and L2. The adjustable capacitor 19 and inductance 2d are set for the electromotive forces induced in the line wires Li and L2 from the auxiliary conductor L l to be substantially degrees out of phase and of substantially the same magnitude as the electromotive forces induced in the line wires LI and L2 due to the communication current from transmitter TN I flowing in the line conductor L3 of the yard communication system. Consequently the unwanted energy created in the line wires L! and L2 due to the communication current used in the yard system is cancelled and balanced out by the energy of the auxiliary output circuit of the transmitter TNl and interference between the yard communication system and the main line communication system is substantially avoided.

Apparatus here disclosed has the advantages that a railroad can be provided with a communication system for use on its main line and also with train communication apparatus for use in a specific local area, such as a yard terminal or test track, and the apparatus used on the main line and the apparatus used for the local area can both operate on the same carrier frequency and interference on the main line system due to the local area apparatus is largely avoided. By use of the same carrier frequency, a locomotive or other vehicle that will find use both on the main line and in the local area, needs to be provided with but a single equipment.

Although I have herein shown and described but one form of transmitting apparatus for inductive carrier railway train communication systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of main track of a railway, a train communication system for said railway using a longitudinal circuit of a line wire extending along said main track as an element of a transmitting channel having inductive relation to circuit elements mounted on a vehicle of a train operating Over said main track, a local area along said stretch and having a track which a train vehicle may occupy, train communication means including a transmitter and a line wire along said local area track for inductive relation with circuit elements mounted on a train vehicle occupying said local area track, said transmitter operable to supply communication current having a given carrier frequency and connected to said line wire of said local area, an auxiliary circuit including an auxiliary line conductor disposed adjacent a given length of said longitudinal circuit and connected to said transmitter, and impedance elements interposed in said auxiliary circuit to determine the magnitude and phase angle of said communication current supplied to the auxiliary circuit for the energy inductively transferred to said longitudinal circuit from said auxiliary line conductor to substan tially balance out the energy inductively transferred inadvertently to said longitudinal circuit from said line wire along said local area track.

2. In combination, a stretch of main track of a railway, train communication means for said railway and including a longitudinal circuit of a pair of line wires extending along said main track for inductive relation with circut elements mounted on a train moving over said main track, a yard of said railway located along said stretch of main track, train communication means for said yard and including a transmitter and a line Wire extending through said yard, said transmitter operable to supply a carrier telephone current and connected to said yard line wire for telephone communication to trains in the yard, an auxiliary circuit including a line conductor mounted parallel to a given length of said pair of line Wires and connected to said transmitter to receive a portion of said carrier telephone current, and means interposed in said auxiliary circuit to determine the magnitude and phase of the carrier telephone current flowing therein to inductively transfer u mounted on a train moving over said main track, w

a yard of said railway located along said stretch of main track, train communication means for said yard and including a transmitter and a line wire extending through said yard, said transmitter operable to supply a carrier telephone current and connected to said yard line wire for telephone communication to trains in the yard; an auxiliary circuit including a capacitor, an inductance and an auxiliary line conductor which is mounted relatively close to and parallel with a given length of said pair of line wires; said auxiliary circuit connected to said transmitter to receive a portion of said carrier telephone current, and said capacitor and inductance proportioned for the electromotive force induced in said pair of line wires due to said carrier telephone current flowing in said auxiliary line conductor to oppose and approximately balance out the electromotive force induced in said pair of line wires due to said carrier telephone current flowing in said yard line wire.

4. In an inductive carrier railway train communication system for a stretch of main line railway track and which system uses the longitudinal circuit of a pair of line wires extending along this stretch of track as an element of a transmitting channel, a local area alongsaid stretch having a track which a train vehicle may occupy, a local train communication system for communication with vehicles on said local area track and including a transmitting channel using a line wire extending along the local.v area track, a transmitter connected to said local area transmitting channel to at times supply communication current thereto, an auxiliary circuit including an auxiliary line conductor disposed adjacent a given length of said pair of line wires, said auxiliary circuit connected to said transmitter to receive a portion of said communication current, and impedance means interposed in said auxiliary circuit to determine the magnitude and phase angle of said portion of said communication current for the energy inductively transferred to said pair of line wires from said auxiliary line conductor to balance out the energy inductively transferred from said local area transmitting channel to said pair of line wires.

5. In an inductive carrier railway train communication system for a stretch of main line railway track and which system uses a transmitting channel including a line circuit that extends along said stretch of main line track, a local area of the railway which includes a track extending a given length adjacent said main line track, an inductive carrier train communication system for said local area and which local area system uses a transmitting channel including a line circuit extending along said local area track, a transmitter having connections to said transmitting channel of the local area system for supplying a carrier communication current thereto, an auxiliary circuit including an auxiliary line conductor mounted parallel to a given length of said line circuit of said main line system, said auxiliary circuit connected to said transmitter to receive a portion of said communication current supplied thereby, and impedance means interposed in said auxiliary circuit to control the magnitude and phase angle of said portion of the communication current supplied to the auxiliary circuit for the energy inductively transferred from said auxiliary line conductor to said line circuit of said main line system to cancel the energy inductively transferred from said line circuit of the local area system to the line circuit of the main line system.

BURROWS C. VAN GILDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

